The Present invention relates to devices and methods for mounting brake pads on disc brake systems of vehicles. In particular, the invention relates to retaining elements that are used to help maintain in position the brake pad during operation.
Modern vehicles of all types, including commercial vehicles such as trucks, buses, etc., utilize disc brake systems to slow down and stop. A typical disc brake system includes a rotating rotor (or disc) that is operatively connected to a wheel or hub of the vehicle, and a non-rotating caliper, fixed to the vehicle, used to press brake pads against the rotor, thus slowing the rotor down and stopping it by friction. As the rotor stops, so does the vehicle.
Various mechanisms and devices are used to retain the brake pad or pads in position relative to the caliper. This prevents undesired movement of the pads while mounting the assembly, during movement of the vehicle and during braking. In this manner, the pads are located and oriented correctly when pistons press them against the rotor. In conventional systems, the brake pad may be held in place using a simple spring that is placed on one edge of the brake pad, and abuts a portion of the caliper assembly. For example, a system of this type is described in European patent EP 00534987 B1, which is incorporated herein by reference in its entirety.
In the conventional arrangements, an example of which is shown in FIG. 1, a leaf spring 15 is pressed by holding brackets 7 against the edges of a pad holder 1 formed in the pad lining. Window-like apertures 21 in the wings 23 of the leaf spring receive holding clips 19 formed on the edge of the pad, to prevent undesired release of the leaf spring 15, and to limit its movement to a certain extent.
According to the present invention, an improved method of retaining the brake pads in position relative to the caliper is provided. In the present invention, an improved resilient element is used to apply a force to the brake pad in a more controlled manner. The resilient element according to the invention is attached to the pad more securely, to better control unwanted displacement in the axial and lateral directions relative to the pad. For example, the resilient element may be a spring element, as will be described in greater detail below.
The exemplary pad retaining spring according to the invention may be formed as an insert that can be fixedly connected to the back plate of the pad. The spring may be placed on the back plate in a pre-tensioned manner, and may be fixed to the top side or edge of the pad by lateral protrusions that extend from the surface of the pad's top side, at the outer edges of the spring. For example, these lateral protrusions may extend from the top edge of the pad back plate at two ends, so that the spring fits lengthwise between the protrusions. This prevents the spring from sliding along the pad back plate in a direction along a length of the spring. In this example the top edge of the back plate houses the spring, however, other sides of the back plate may be used, depending on where a pad retaining clamp of the disc brake is applied.
To prevent lateral slipping and unintended removal of the spring, one or more protrusions may be formed generally at the center of the top side of the pad back plate, and may extend through openings or windows formed in a surface of the spring. After mounting the spring on the pad back plate, the protrusions can be clenched, or plastically deformed to expand in a direction parallel to the spring, to lock the spring in place. Alternatively, rivet-like elements may be used for the protrusions. This process protects the spring against loss or inadvertent removal. It also provides a reliable guide to the movement of the spring against the pad back plate, so that lateral movement thereof is controlled.
According to exemplary embodiments of the invention, the spring is shaped so that unwanted movement relative to the pad along its length axis, in this case along the top edge of the pad, is minimized. The force of the spring, or other resilient element, is generated when two discrete lever arms are elastically deformed by, for example, the pad retaining clamp or lever that is used to lock the pad in place within the caliper. The force is then transmitted to the pad's back plate by a base of the resilient element, which extends along substantially the entire length, or at least a majority of the top surface of the back plate. In a different embodiment, more than one resilient element may be used for each back plate of a brake pad, depending in part on the geometry of the pads and the desired force to be applied to the back plate. A resilient force is thus applied to the brake pad by the resilient element, so that the pad is urged in a desired position relative to the caliper.
In one exemplary embodiment, the resilient element is a spring shaped like a compressed “U”, in which the two legs are bent inward towards the base at end points of the spring, so that when compressed, the legs become generally parallel to the base.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.